1. Field of the Invention
The present invention relates to an apparatus for laser surgery on a cornea, in which a laser beam ablates away a surface of a cornea to correct the refractive error of an eye.
2. Description of Related Art
There is a known method for correcting the refractive error of an eyeball by removing away stroma underlying epithelium of the cornea in a lens-like shape by a laser beam to change its curvature. This can be called Photorefractive Keratectomy. In a conventional surgery method, the epithelium constituting the anterior surface of the cornea would be peeled off in advance of irradiation of a laser beam thereto. This peeling method of the epithelium from the cornea was a mechanical method using a hockey knife and the like to scrape the epithelium.
In such a mechanical removing method with a hockey knife and the like, the time needed for removing the epithelium of the cornea would differ from operator to operator according to each skill and others, this influencing the dry condition of the stroma of the cornea and causing a change of the moisture content of the stroma. Accordingly, there occurs a problem that, if an excimer laser beam which is high absorbable into water is used for ablating the stroma of a cornea, change of a dry condition of the stroma causes large variations in ablation depths on the stroma. As a result, the actual ablated shape of the stroma of the cornea differs from a predetermined shape of the stroma, resulting in errors in the corrected refractive power of the postoperation cornea.